ITMI951399A1 - PROCEDURE FOR THE PREPARATION OF CRYSTALLINE VINYLAROMATIC POLYMERS WITH A PREDOMINANTLY SYNDIOTACTIC STRUCTURE - Google Patents

Abstract

Process for the preparation of crystalline vinyl aromatic polymers with a predominantly syndiotactic structure which includes polymerizing the vinyl aromatic monomers in the presence of a catalytic system consisting essentially of: a) a titanium complex of formula (I): (FORMULA I) where R and R ' , equal or different, represent an aliphatic radical C1-C12 or aromatic C2-C10 while n is an integer that is worth 3 or 4; b) a cocatalyst chosen from aluminoxane and a boron compound of formula (II): (FORMULA II ) wherein X1, X2 and X3, equal or different from each other, represent a C1-C20 perfluorinated hydrocarbon radical.

Description

DESCRIPTION

The present invention relates to a process for the preparation of crystalline vinyl aromatic polymers with a predominantly syndiotactic structure.

More particularly, the present invention relates to a process for the preparation of crystalline polystyrene in which the polymeric chains have an essentially syndiotactic configuration.

Polystyrene is a thermoplastic polymer obtained by radical polymerization of styrene and is used in the production of printed articles, films, electrical materials, packaging materials, etc. It is an atactic, amorphous, dated polymer with excellent insulating properties and moderate thermal resistance. However, for many applications it is preferred to have crystalline materials, with high thermal and solvent resistance, characteristics which atactic polystyrene does not possess.

European patent EIO.615 discloses a polystyrene having a structure characterized by a high degree of stereoregularity, in which the phenyl substituents are arranged to provide a syndiotactic polymer. This material does not have the aforementioned drawbacks of atactic polystyrene as it is crystalline and therefore, once transformed, can be subjected to orientation processes, is insoluble in almost all organic solvents and has a melting temperature in the 260-280 range. ° C, so that it has a high thermal resistance, comparable or superior to that of thermoplastic condensation polymers (polyesters, polyamides, polyimides, etc.).

The syndiotactic polystyrene can be prepared according to what is described in the literature, for example according to what is described in the European patent EP E7S.584 or in the US patent 4.976.730, by polymerization catalyzed by compounds of Ti, Zr, V, Ni, in the presence of a cocatalyst represented by methylailuminoxane (a mixture that can contain cyclic, linear and cage oligomers, containing the repeating unit —AICH3O-) or, as described in published European patent application 42 1.659, by derivatives of boron containing fluorinated groups.

Examples of catalysts for syndiotactic polystyrene synthesis distributed in literature are titanium halides (chloride, bromide, etc.), titanium alcoholates (methoxide, ethoxide, propoxide, isopropoxide, butoxide, etc.), titanium carboxylates, metallocenes ( cyclopentadienyl titanium trichloride, cyclopentadienes1 titanium dichloride, pentamethy1cyclopentadienes 1 titanium trichloride, cyclopentadienyl titanium alkoxides, cyclopentadienyl titanium alkyl1i9 pentamethylcyclic lopentadienes1 titanium alkyl, titanium dicyclopentanium, titanium dihydrogen1 titanium ) and the corresponding zirconium compounds.

The Applicant has now found that it is possible to synthesize crystalline vinyl aromatic polymers, and in particular crystalline polystyrene, having a predominantly syndiotactic configuration using a new catalytic system which has never been described in literature. The catalysts of the present invention also have the property of giving polymers with higher degrees of stereoregularity and much higher molecular weights than polymers obtained with traditional catalysts. For example, it is possible to obtain polystyrene with a degree of stereoregularity higher than 79.5K and with weight average molecular weights Mw higher than 300,000, generally between 300,000 and 500,000.

Therefore, the object of the present invention is a process for the preparation of crystalline vinyl aromatic polymers with a predominantly syndiotactic structure which then comprises interlinking the vinyl aromatic monomers, alone or in mixture with at least one other copolymerizable ethylenically unsaturated monamer, in the presence of a catalytic system consisting of essentially from:

a) a titanium complex of formula (I):

where R and R ', equal to or different from each other, represent an aliphatic C1-C12 or aromatic radical C6-C20 while n is an integer that is 3 or 4;

b) a cocatalyst selected between aluminoxane and a boron compound of formula (II):

The general Tormula titanium catalyst (I) is a known product described in "Chemische Berichte" ISO, 955 <(> 19B7) or in "Journal of the Chemical Society: Dalton Transactions", 693 (1991). These products can be prepared by tacitly reacting titanium tetrachloride or trichloride with carbon dioxide and an aliphatic or aromatic diamaiine.

Non-limiting examples of general Tormula (I) titanium catalysts particularly suitable in the present invention are:

The molar ratio between aromatic wine manomer and titanium is not particularly critical but can vary between 1000 and 100,000, preferably between 5,000 and 50,000.

The aluminoxane cocatalyst consists of a mixture that can contain linear or cyclic structures, as well as any cage structures. The linear structure has general formula (III):

while the cyclic structure has the general formula (IV /):

The aforementioned cocatalizers, of general formulas (III) and (IV), are known in the literature and described, for example, in published European patent applications 272.584 and 421.659 or in US patent 4.978.730.

Co-catalyst of general formula (II), actually its salt, is known in literature and is described in published European patent applications 421.659 and 482.934

Preferred cocatal ysts of general formulas (II), (III) or (IV) are tris (pentafluorophenes 1) boron or tetra (pentafluoroferii1) borate of organic cations such as triphenyl carbon, ammonium, phosphonium, etc. and methylal luminoxane with number average molecular weight Un between 400 and 2000. Generally the cocatalyst is used in quantities such that the aluminum / titanium molar ratio is between 50 and 2000 or such that the boron / titanium ratio is between 0.5 and 5.

According to the process object of the present invention, the catalytic system described above can also comprise an alkyl aluminum in which the alkyl group contains from 1 to 6 carbon atoms, for example trimethyl aluminum, triethyl aluminia, tri isobutyl aluminum, etc., in such quantities that the molar ratio of aluminum alkyl / titanium is between 0 and 1,000.

The term "vinyl aromatic polymers" as used in the present description and in the claims essentially means the polymers of styrene and of the derivatives of styrene and the relative copolymers containing up to 20 / · in moles of another terminally polymerizable monomer selected from those of formula general (V):

wherein R2 represents a hydrogen atom or a C1-C6 alkyl radical, a C4.-C12 or aromatic cycloalkyl radical.

Derivatives of styrene include alkyl styrenes, in which the alkyl group contains 1 to carbon atoms, halogenated styrenes, C1-C4.-alkoxy styrenes, carboxy styrenes, wines Naphthalenes, such as alpha- or beta-wines1 naphthalene , vinyl tetrahedron naphthalene such as 1, 2,3,4-tetrahydro-6-wine 1 naphthalene, etc. Typical examples of substituted styrenes are pmethylstyrene, m-methylstyrene, alone or in a mixture with each other, ethylstyrene, butylstyrene, p-tert-butylstyrene, dimethylstyrene, chorostyrene, bramase irene, fluorost irene, chloromethylstyrene, methoxyst irene , acetaxis methylstyrene, etc. The polymerization reaction can be carried out in bulk or in solvent. In this second case, the solvent can consist of aliphatic or aromatic hydrocarbons or their mixtures and is used in quantities such that the solvent / monomer volume ratio is between 0 and 100. The preferred solvent is toluene.

More specifically, according to the general procedure adopted for this type of reaction, before polymerization the monomers of aromatic wines are subjected to treatments aimed at eliminating catalytic poisons, such as phenolic stabilizers, water, phenol-acetylene, and consisting in distillation, passage on columns containing activated molecular sieves or activated alumina, etc. The monomers and, optionally, the solvent are loaded into the reaction apparatus together with the optional alkyl aluminia and the cocatalyst. After a time varying between 5 seconds and 30 minutes, a solution of the titanium derivative of general formula (I) is added. The reaction proceeds for times ranging from 13 minutes to 20 hours at temperatures between 0 and 110 ° C. At the end, the obtained polymer is recovered according to traditional methods.

In order to better understand the present invention and to put it into practice, some illustrative but not limiting examples are given below.

Analysis procedures

- The percentage of syndiotactic polymer is determined by extracting the polymer with acetone or methylethylketane (MEK) at boiling for 10-10 hours.

- The degree of stereoregularity is determined by carbon 13 nuclear magnetic resonance spectroscopy as described in U5A 4,680,353.

- Thermal transition temperatures <Tm = melting temperature, Tg = glass transition temperature are determined by differential scanning calorimetry.

- The molecular weights of the obtained polymers were determined by Gel Permeation Chromatography in 1, E, 4-trichlorobenzene at 135 ° C.

EXAMPLE 1

SD ml of styrene, purified by passage on a basic alumina column, and 1.2 ml of a 1.57 M solution in toluene of methylailuminoxane were introduced in an inert atmosphere into a coded test tube. After 5 minutes, S, E6 ml of a 0.00575 µl solution in toluene of titanium tris (diisopropylcarbamate) were introduced.

The reaction was carried out for 5 hours at 60 ° C. At the end, the mixture was suspended in 100 ml of methanol, containing E ml of concentrated HCl, and filtered. The solid was suspended again in methanol, filtered and dried under vacuum. 2.24 g (yield 15.3%) of syntactic polystyrene were obtained.

Insoluble fraction in methylethylketone (MEK): 76.4%.

13-C NMR analysis shows that the polymer has a percentage of syndiotactic dyads of 99.5%.

EXAMPLE 2

S0 ml of styrene, purified by passage on a basic alumina column, and 0.8 ml of a 1.57 K solution in toluene of methylauminoxane were introduced in an inert atmosphere into a tailed test tube. After 5 minutes E, E6 ml of a 0.00275 M solution in toluene of titanium tris (diisoprapylcarbamate>.

The reaction was carried out for 5 hours at 6D ° C. At the end, the mixture was suspended in 800 ml of methanol, containing 2 ml of concentrated HCl, and filtered. The solid was suspended again in methanol, filtered and dried under vacuum. 1.02 g (yield 5.6%) of syntactic polystyrene were obtained.

Insoluble fraction in methylethylketone (MEK) at 68.5%.

13-C NMR analysis shows that the polymer has a percentage of syndiotactic dyads of 99.6%.

EXAMPLE 3

80 ml of styrene, purified by passage on a basic alumina column, and 2.4 ml of a 1.57 M solution in toluene of methylaluminoxane were introduced in an inert atmosphere into a tailed test tube. After 5 minutes, 5.75 ml of a 0.00817 M solution in toluene of titanium tris (diisopropylcarbamate) were introduced.

The reaction was carried out for 5 hours at 60 ° C. At the end, the mixture was suspended in 800 ml of methanol, containing 8 ml of concentrated HCl, and filtered. The solid was suspended again in methanol, filtered and dried under vacuum. 1.72 g (yield 9.5%) of syndiotactic polystyrene were obtained

Insoluble fraction in methylethylketone (MEK): 81.67 ·.

13-C NHR analysis shows that the polymer has a percentage of synotactic dyads of 99.5%.

EXAMPLE

20 ml of styrene, purified by passage on a basic alumina column, and 1.2 ml of a 1.57 M solution in toluene of methylaluminoxane were introduced in an inert atmosphere into a tailed test tube. After 5 minutes 3.0 ml of a 0.00211 M solution in toluene of titanium tetrakis (diisopropylcarbamate>.

The reaction was carried out for 5 hours at 60 <e> C. At the end, the mixture was suspended in 200 ml of methanol, containing 2 ml of concentrated HCl, and filtered. The solid was suspended again in methanol, filtered and dried under vacuum. 3.02 g (yield 16.5%) of syndiotactic polystyrene were obtained.

Insoluble fraction in methylethylketone (MEK): 71.5%.

13-C NMR analysis shows that the polymer has a percentage of synotactic dyads of 99.5%.

EXAMPLE 5

69 ml of styrene were introduced in an inert atmosphere into a one-liter reactor, purified by passage on a basic alumina column. The styrene was brought to 60 ° C and 7 ml of a 1.57 M solution in toluene of methylalumoxane and 165 mg of titanium tetrakisidi isopropylcarbamate) dissolved in 60 ml of toluene were added.

The reaction was carried out for 5 hours at 60 ° C. At the end, the mixture was suspended in 1 1 of ethanol, containing 8 ml of concentrated HCl, and filtered. The solid was suspended again in ethanol, filtered and dried under vacuum. 94.3 g (14.9X yield) of syndium tactical polystyrene were obtained.

Insoluble fraction in methylethylketone (MEK): 84.83⁄4.

The 13-C NMR analysis shows that the polymer has a percentage of syndiotactic dyads of 97.6%.

Thermal properties: Tm = 667 ° C; Tg = 99 ° C.

Weight average molecular weight Mw: 348,000.

Molecular weight medion numeral Mns 155,000.

COMPARATIVE EXAMPLE

Under experimental conditions similar to those of Examples 1 and 4, a polymerization was carried out using the cyclopentadienes Ititaniotrichloride.

5.98 g (yield 36.9X1 of tactical polystyrene syndium was obtained.

Fraction insoluble in methylethylketone (MEK) 87.0%.

13-C NMR analysis shows that the polymer has a percentage of syndiotactic dyads of 98.1%.

Claims (1)

CLAIMS 1) Process for the preparation of crystalline vinyl aromatic polymers with a predominantly syndiotactic structure which comprises polymerizing the vinyl aromatic monomers, alone or in mixture with at least one other ethylenically unsaturated monomer copolymerizable in the presence of a catalytic system essentially consisting of: a) a titanium complex of formula <I>: 2) Process according to claim 1, wherein the molar ratio of vinyl aromatic monameral to titanium is comprised between 1,000 and 100,000. 3) Process according to claim 1 or 2, wherein the cocatalyst is used in quantities such that the aluminum / titanium molar ratio is between 50 and 2000 or such that the boron / titanium ratio is between 0.5 and 5. 4) Process according to any one of the preceding claims, in which the catalytic system comprises an aluminum alkyl in which the alkyl group contains from 1 to 6 carbon atoms. 5) Process according to claim 4, in which the molar ratio of aluminum alkyl / t itanium is comprised between 0 and 1,000. 6) Process according to any one of the preceding claims, in which the polymerization reaction is carried out in bulk or in solvent. 7. Process according to claim 6, wherein the solvent is used in quantities such that the solvent / monomer volume ratio is between 0 and 100. 8) Process according to any one of the preceding claims, in which the polymerization is carried out at temperatures between 0 and 110 ° C.